Consistancy and freeness measuring and regulating apparatus for thin stock pulp and paper



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I H |L EI 7 VALVE //V VE N 70/? United States Patent Ofi ice 3,110,172 Fatented Nov. 12, 1963 CONSISTEN CY AND FREENESS MEASURING AND REGULATING APPARATUS FDR THIN STOCK PULP AND lAPER William C. Irwin, Pointe Claire, Quebec, Canada, assignor to Process & Steam Speciaities Inc, Montreal, Quebec, Canada Filed Mar. 6, 1961, Ser. No. 93,713 Claims. (Cl. 73-54) The present invention relates to fluid stock regulators and more particularly to an improved consistency and freeness regulator particularly suited for use in the pulp and paper industries.

There are many and varied types of stock regulators at present available, many of which are capable only of a relatively restricted application since they are designed to control consistency and/ or ireeness of stock at certain specific stock preparing or paper making operations. For example, the effective regulation of thin stock 'helow approximately 1.5% presents certain problems and in most cases with existing regulator equipment regulation as to consistency only takes place at further operations, for example at the thickener Where consistencies are generally higher than 2%.

The present application recognizes these and other problems and as a solution aims to provide a versatile stock regulator construction which is suitable for application on all types of pulp. These include thin sulphite, groundwood, 'kraft, sulphate, soda and so on, in addition to mixtures of these pulps such as newsprint, fine paper furnishes, etc.

More specifically, the regulator of the invention consists essentially of a container or tank that is divided into a main chamber and an overflow chamber by suitable partitions with the main chamber being divided by a suitable baflile or weir into an intake compartment and an admitted stock compartment. A stock intake manifold leads directly into and across the intake compartment so as to be adapted to deliver a constant flow of stock. The bafille between the stock intake and admitted stock compartment is provided with an opening masked by a screen disk or perforated plate so that a constant flow is maintained through the baflie between the two compartments. The partition forming one transverse or end Wall of the stock intake compartment is provided with a suitable stock outlet orifice controlled by an adjustable gate to provide a means of regulating stock lever, and the opposing side wall is provided with a fixed weir, the excess stock flowing over the weir into the overflow chamber. The partition between the overflow chamber and the admitted stock compartment is also provided with an opening controlled by an adjustable weir so as to provide a means of controlling stock level. The overflow as before spills into the overflow chamber which is provided with a discharge outlet in the'usual manner. Means in the form of rotating blades or rods are provided preferably, at each side of the screen for the purpose of a pressure foil cleaning action by creating pulsations 'across the screen.

In operation, the stock is fed through the inlet into the stock compartment where a head is maintained by adjustment of the outlet orifice and the fixed weir. The stock flows through the screen into the admitted stock compartment and, as mentioned above, at a predetermined level, also discharges over a weir. It should be mentioned that the screen disk or perforated plate is not intended to serve as a screening or classifying device but rather to provide an impedance to fluid flow from intake compartment to admitted stock compartment which will vary with consistency, freeness, drainage rate and other characteristics of the stock. All of the stock delivered to the prescut reguator eventually is discharged to the common overflow chamber and out of the discharge outlet so whatever is fed into the regulator has to go out in unchanged condition. By selection of the gauge or perforations of the screen disk, and weir adjustment, measurements can be made selectively and continuously of any variable such as consistency, freeness, drainage rate, etc.

In this construction, the flow of the fluid through the screen establishes a proportional differential head across the screen. The differential head is preferably measured with air purged bubble tubes feeding a differential pressure transmitter which gives a proportional pneumatic output, though other comparative means could be utilized.

Having thus generally described the nature of the invention, particular reference will be made to the accompanying drawings illustrating preferred embodiments thereof, and in which:

FIGURE 1 is a view in plan of a stock regulator in accordance with the invention.

FIGURE 2 is a front elevation of the construction shown in FIGURE 1.

FIGURE 3 is a cross-sectional view of FIGURE 1 along the line 33.

FIGURE 4 is a cross-sectional view of FIGURE 1 along theline 44.

FIGURE 5 is a cross-sectional view of FIGURE 3 along the line 5-5.

FIGURE 6 is a cross sectional view of FIGURE 4 along the line 6-6 to show the construction of the adjustable gates in more detail.

FIGURE 7 is a diagrammatic illustration of one application of a stock regulator in accordance with the invention as a means of maintaining thin stock consistency ahead of the usual screens.

With particular reference to FIGURES 1 and 2 of the drawings the stock regulator of the invention is shown as consisting of a main tank 10 divided into a main chamber 12 and an overflow chamber 14. The main chamber 12 is divided into an inlet stock compartment or chamber 16 and an admitted stock compartment or chamber 18 by a removable baffle plate 19 mounted in grooved slides 1911. Stock inlet manifold 26 leads into the stock chamber 16 and is provided with a plurality of stock discharge orifices 22 and at least one elongated slot 23.

The thin pulp or paper stock sample to he regulated enters distribution manifold 20 and flows into chamber 16 through the series of holes 22 and slot 23 in the manifold. It is to be noted that the holes 22 are all disposed below the transaxial or diame-trical center line of the manifold 20 so that as the stock is discharged through these orifices it is directed towards the bottom of the compartment avoiding turblence within the chamber 16. The elongated slot or slots 23 are disposed along the lowest portion of the manifold 20 to ensure complete drainage when the apparatus is shut down for cleaning or maintenance. The level rises until stock flows over fixed weir 24, which is cut into one side of the partition 21 defining the outer wall of chamber 16. This overflow over weir 24 establishes a constant level in chamber 16. Excess sample, that is to say, stock that can not discharge through the orifices 22, 23 due to the rate of flow, flows through manifold 21) and "discharges directly to the overflow chamber 14 through a concentric opening 40 in a baflle plate 44 forming the transverse end wall or partition to the chamber 16, 13. A V notch gate 45 is adjustable in slides 46 secured to the baflle plate 44 and acts to control the flow through the orifice 40.

With reference to FIGURE 3, the open end 21 of manifold 20 is fitted closely to baflle 44, but is not attached to it. The space between the manifold outlet end 21 and the baffle 44 being at all times preferably no greater than the maximum dimensions of the outlet opening 22. A small shield 47 is attached to bathe 44-, to deflect leakage flow from the end 21 of the manifold 20 and further prevent surface turbulence in chamber 16. By throttling a hand valve (see FIGURE 6, for example) ahead of the regulator in conjunction with gate 45, it is possible to take any desired portion of the total flow in the sample line through the regulator and maintain a constant discharge over weir 24. As also shown most clearly in FIGURE 3 adjustment of the gate 45 is obtained through the screw handle 49 bearing against the bafile 44. It should also be noted that a purge orifice 49 is provided in the battle plate 44 directly in alignment with the gate 45. The gate 45 due to its V shaped end never blocks the orifice 49' so that a constant stream of stock to the outlet chamber 14 provides a means of carrying out any splinters, knots or other foreign material which might tend to pile up and blockthe main discharge orifice 40.

A screen plate 28 consisting of a'perforated, slotted, or wire mesh disk is mounted in the baffle plate 19 which separates chambers 16 and 18; Bafile plate 19 as previously mentioned is mounted in slides indicated at 19a and may be removed for mounting or servicing the screen plate. The blade shaft 51 must be withdrawn first before plate 19 can be removed.

As shown most clearly in FIGURES l and 2, the shaft 51 extends through and is journalled in suitable bearings 60 mounted on the exterior plates of the tank 10. A drive pulley 80 is mounted on the shaft 51 and is driven through drive belt 81 from a suitable motor 84.

The stock or filtrate flows from chamber 16, through screen 28 and fills chamber 18 and then flows out over an adjustable gate or weir also provided in the bafile 44. The adjustable gate or weir 25 is mounted in slides 25a and is adjusted as to height by means of a screw handle 27 having one end bearing against the bafiie 44. The level in chamber 16 comes to equilibrium when the difierential head between chambers 16 and 18 is just sufiicient to maintain a constant rate of flow through screen plate 28 and therefore a constant discharge head over weir 25. By adjusting the level of 'Wcir 25, the optimum rate of flow through screen 28 for a given discharge head over weir 25 can be obtained. This adjustment will be explained later.

The function of screen 28 is to provide impedance to fluid flow which will vary with consistency, freeness, drainage rate and other characteristics of the stock. By proper selection and adjustment of weir 25, runner blade shaft 51 r.p.m., screen plate 28 perforation size or mesh, and the provision of the blades 53, 54 mounted on the shaft 51 at one or both sides of the screen 28, the diiferential level between chambers 16 and 18 will always be proportional to the variable being measured.

The purpose of blades 53 and 54 is to provide a series of pulsating and oscillating pressure waves across screen plate 28. A fibre mat will tend to increase on screen plate 28 due to drainage and dewatering, but the pressure waves created by the blades 53, 54 tend to strip this mat away. The overall effect is a constant fibre mat thickness on the screen plate 28 and continuous operation without plugging screen plate 28.

All effluent, whether passing through screen plate 28 or not, discharges from various points into overflow chamber 14 and then discharges from the regulator through discharge connection 66.

The difierential head in chambers 16 and 18 is measured with standard bubble pipes 96 and 97 mounted in slide tubes 98, 9.9. The bubble pipe pressure feeds into a standard industrial pneumaticdifferential transmitter (not illustrated) which in turn transmits a 3 to '15 psi. pneumatic signal. The bafile plate 44 is mounted in slides 44a for easy removal for cleanups. Gate and weir 25 settings are unchanged during cleanup.

A control application of the regulator construction described is shown diagrammatically in FIGURE 7 to maintain thin stock consistency ahead of screens. A sample flow is fed to the regulator A continuously under the control of a valve T and the effluent discharged to a convenient sump B. As the consistency increases, the difterential level measurement will increase, giving an increased output from the pneumatic transmitter C. This signal is used with conventional instrumentation D to control a dilution valve E at the pump suction. Dilution water flow is increased until the consistency is controlled at the desired value. Other instrumentation shown complements the control system described. A pressure con- ;troller F throttles a bypass valve G to maintain a constant sample line flow and also gives stability for the level control system. A level control H and valve I act to regulate demand to the screen head box I.

There are many advantages in the present regulator construction over prior art constructions of this nature. For example:

(1) Coarse pilot screening action in passing the stock from the manifold 20 to inlet chamber 16 through large (approximately 1 1) holes and slot 22, removes large knots and wood splinters and large [foreign objects which might damage or plug up the screen 23 when using the regulator on unknotted stock and the like, but this removal of large material in no way alters the characteristics of the pump to be measured.

(2) A high velocity through the inlet and inlet manifold 20 purges foreign objects and makes the manifold largely self-cleaning.

(3) Total sample flow rate can be conveniently varied, by the gate 45 to compensate for long sample lines and inherent time lag.

(4) The manifold 20 assures uniform and rapid distribution of the stock sample to the measuring element.

(5) The gate 45 adjustment, when used with an external throttling valve on the sampling line will almost always dampen out pulsations in sample line pressure to the point where auxiliary head boxes are unnecessary ahead of the regulator.

(6) Mechanical features include a blade 53 or 54 on one or both sides of the screen to give a pressure foil cleaning action by creating pulsations across the screen. The rpm. of these foils are varied to meet the requirements of a specific application.

(7) The end baflie plate 44 is slide mounted and can be lifted or removal by hand without tools for cleaning the box and then replated without disturbing the settings of the weir or gate.

(8) The screen mounting plate or bafile 19 is slide mounted and can be removed, after removing the runner shaft 51, for servicing the screen conveniently.

(9) The bubble pipes 96, 97 are mounted in adjustable sleeves. This gives a convenient method of zero setting the transmitter output signal.

In addition to the above-noted advantages the regulator of the invention can be used for example in the following applications:

I (a) On knotted or unknotted chemical pulp as a consistency or screenability controller ahead of the primary screens.

(b) On groundwood stock consistency control after grinder pits.

(c) Drainage control on the paper machine Fourdrinier wire.

(d) Direct thin stock consistency measurement on paper machine head box stock and incorporated into an automatic basis weight control system.

(e) Continuous measurement of freeness.

I claim:

1. A constant flow fluid stock regulator comprising, a stock tank, a plurality of vertical partitioning walls with in said tank dividing the interior into a stock inlet chamber, an admitted stock chamber, and a stock discharge chamber, a stock inlet manifold leading into and extending across said stock inlet chamber and including a plurality of stock outlet openings along its length adapted to supply stock to said inlet chamber, at least one stock discharge opening in one partitioning wall defining said stock inlet chamber and leading to said stock discharge chamber, a stock outlet in a further one of said partitioning walls between said stock inlet chamber and said admitted stock chamber and a perforated baffle masking said stock outlet adapted to admit a continuous flow of stock from said inlet chamber to said admitted stock chamber, rotatably mounted means positioned within said tank spaced from said baified stock outlet and adapted to create a pulsating cleaning action to the perforated bafile masking said stock outlet, the remaining partitioning walls defining said inlet chamber and admitted stock chamber having weirs leading to said discharge outlet chamber, a first stock consistency measuring means positioned within said stock inlet chamber and a second stock consistency measuring means positioned within said admitted stock chamber, said first and second consistency measuring means being operatively connected to a differential signal transmitter, whereby the diflerential head between said inlet and admitted stock chambers as created by the impedance to fluid flow by the said baffled stock outlet is constantly measured and a regulating action provided to said difierential signal transmitter.

2. A fluid stock regulator comprising, a stock tank, a plurality of vertical partitioning walls within said tank dividing the interior into a stock inlet chamber, an admitted stock chamber, and a stock discharge chamber, a stock inlet manifold leading into and across said stock inlet chamber and including a plurality of stock outlet openings along its length and an open end terminating short of one partitioning wall defining said stock inlet chamber, a stock discharge opening in said partitioning Wall leading to said stock discharge chamber, a screened stock outlet in a further one of said partitioning walls extending between said stock inlet chamber and said admitted stock chamber adapted to admit a continuous flow of stock from said inlet chamber to said admitted stock chamber, rotatably mounted means positioned Within said tank spaced from said screened stock outlet and adapted to create a hydraulic pressure wave applying a pulsating cleaning action to the screen masking said outlet whereby a stock fibre layer deposited on said screen by said outlet flow is maintained at a substantially constant thickness proportionate to the characteristic of said stock, the remaining partitioning walls defining said inlet chamber and admitted stock chamber having weirs leading to said discharge outlet chamber, a first stock consistency measuring means positioned within said stock inlet chamber and a second stock consistency measuring means positioned within said admitted stock chamber, said first and second consistency measuring means being operatively connected to a differential signal transmitter, whereby the differential head between said inlet and admitted stock chambers as created by the impedance to fluid flow by the said screened stock outlet is constantly measured and a regulating action provided to said difierential signal transmitter.

3. A constant flow fluid stock regulator as claimed in claim 2, wherein said stock discharge outlet in said inlet chamber partitioning wall is adjustable as to dimensions and is located in axial alignment with and adjacent to said inlet manifold open end.

4. A constant flow fluid stock regulator as claimed in claim 2, wherein said first and second consistency measuring means comprises bubble pipes leading into said inlet chamber and screened stock chamber respectively, and said difierential signal transmitter comprises a pneumatic differential transmitter adapted to transmit a pneumatic pressure impulse.

5. A constant flow regulator as claimed in claim 2, wherein the open end of said inlet manifold is spaced from said partitioning wall a distance no greater than the maximum dimensions of any of said inlet manifold stock outlet openings whereby foreign objects of a greater size than said outlet openings are contained within said manifold and delivered through said wall orifice to said stock discharge chamber.

References Cited in the file of this patent UNITED STATES PATENTS 810,020 Applegate Ian. 16, 1906 2,027,660 Wells Jan. 14, 1936 2,302,327 Kehoe et a1 Nov. 17, 1942 2,615,329 Witham Oct. 28, 1952 

1. A CONSTANT FLOW FLUID STOCK REGULATOR COMPRISING, A STOCK TANK, A PLURALITY OF VERTICAL PARTITIONING WALLS WITHIN SAID TANK DIVIDING THE INTERIOR INTO A STOCK INLET CHAMBER, AN ADMITTED STOCK CHAMBER, AND A STOCK DISCHARGE CHAMBER, A STOCK INLET MANIFOLD LEADING INTO AND EXTENDING ACROSS SAID STOCK INLET CHAMBER AND INCLUDING A PLURALITY OF STOCK OUTLET OPENINGS ALONG ITS LENGTH ADAPTED TO SUPPLY STOCK TO SAID INLET CHAMBER, AT LEAST ONE STOCK DISCHARGE OPENING IN ONE PARTITIONING WALL DEFINING SAID STOCK INLET CHAMBER AND LEADING TO SAID STOCK DISCHARGE CHAMBER, A STOCK OUTLET IN A FURTHER ONE OF SAID PARTITIONING WALLS BETWEEN SAID STOCK INLET CHAMBER AND SAID ADMITTED STOCK CHAMBER AND A PERFORATED BAFFLE MASKING SAID STOCK OUTLET ADAPTED TO ADMIT A CONTINUOUS FLOW OF STOCK FROM SAID INLET CHAMBER TO SAID ADMITTED STOCK CHAMBER, ROTATABLY MOUNTED MEANS POSITIONED WITHIN SAID TANK SPACED FROM SAID BAFFLED STOCK OUTLET AND ADAPTED TO CREATE A PULSATING CLEANING ACTION TO THE PERFORATED BAFFLE MASKING SAID STOCK OUTLET, THE REMAINING PARTITIONING WALLS DEFINING SAID INLET CHAMBER AND ADMITTED STOCK CHAMBER HAVING WEIRS LEADING TO SAID DISCHARGE OUTLET CHAMBER, A FIRST STOCK CONSISTENCY MEASURING MEANS POSITIONED WITHIN SAID STOCK INLET CHAMBER AND A SECOND STOCK CONSISTENCY MEASURING MEANS POSITIONED WITHIN SAID ADMITTED STOCK CHAMBER, SAID FIRST AND SECOND CONSISTENCY MEASURING MEANS BEING OPERATIVELY CONNECTED TO A DIFFERENTIAL SIGNAL TRANSMITTER, WHEREBY THE DIFFERENTIAL HEAD BETWEEN SAID INLET AND ADMITTED STOCK CHAMBERS AS CREATED BY THE IMPEDANCE TO FLUID FLOW BY THE SAID BAFFLED STOCK OUTLET IS CONSTANTLY MEASURED AND A REGULATING ACTION PROVIDED TO SAID DIFFERENTIAL SIGNAL TRANSMITTER. 